Tag Archives: tips

Stacking: the Overloaded Word That Needs Explanation

The current rage of “stacked Milky Way” (or night sky) captures is quite different from the star trail or timestacks style of captures. Huh? The words stack and stacking are overloaded with many different meanings. Let’s see if we can add some precision and clarification.

Here are some of the variations possible:

  • Auto Blend Layers with Stacking: Used for macro/focus stacking, HDR, and generic image blending – NOT for astro images!
  • Lighten Mode Stacking: Creating Star Trails!
  • Statistics Mode Blending (Stacking): Can perform the same operation as Lighten Mode Stacking when the option “Maximum” is used, however Statistics are heavy weight and more complicated to do in our opinion.
  • Align and Stack: Deep sky astrophotography using several images taken one after another as quickly as possible. Photoshop doesn’t do this well, but we describe how in the next section. Align is the distinguishing word here.
  • Tracked Stacked Images: For still astrophotography images with less noise and greater detail. A device is required that tracks the sky rotation – the word tracked is the key here.

    Adobe Lightroom and Adobe Bridge “Stacking”

  • Group into Stack:  Not stacking at all! It really just means “create a group”.

The above is NOT an exhaustive list of the kinds of stacking you may hear about!

Stacking Types Explained

Group into Stack

Let’s start with the easy one: Stacking may mean add to group. In Lightroom and Adobe Bridge you can pick several photos and the options  Stacking -> Group into Stack. Or pick several photos and either Photo Merge to HDR or Panorama with the “Create Stack” option checked. In this context, Stacking and Stack just means group.  Unfortunately a photo can only appear in one stack, and you cannot stack photos from different folders together.

Why would you want a photo to appear in two (or more) stacks groups? Here is an example where I used a single top shot and created two different panoramas.

Panoramas 1 and 2 were both created using image 3 (608095.NEF) but when panorama 2 was created, image 3 was removed from the stack (group) for 1 and added to the stack (group) with 2. Furthermore, you can see that the panorama and the two photos used to create it were all added into the group (notice the last image says 3 of 3).

Blend Layers using Lighten Mode

Stacking may mean blend photos in lighten or darken blend mode – examples are star trails and timestacks. In this usage, the lightest (or darkest) of all the pixels in each image is selected. This is the kind of stacking that AdvancedStacker Plus does. Below is an example of taking several images that we collected over time with long delays between each exposure causing the “dotted” appearance of the star trail.

Several layers of images taken at intervals all set to blend mode “Lighten”

Align and Blend Stacking

Stacking can ALSO mean ALIGN and blend images with median, mean (aka average) or more sophisticated algorithms. Indeed astroimagers have been doing this style of blending for years using techniques that involve “star registration” (aligning stars with stars) and some pretty fancy stacking algorithms like Alpha-Kappa Median Clipping and Entropy Weighted Average. The key point here is the alignment. Indeed, here at StarCircleAcademy, we’ve explained how you can brighten and reduce noise in your foreground using simple astrophotography processing techniques.  See below for how to accomplish Align and Blend Stacking in Photoshop, and plenty of warnings about why this method is very likely to FAIL using Photoshop as the tool.

You may also see references to tracked, stacked images. These are the same as “align and blend” just described, except that to capture the image, the camera is guided by an external device (or by some fancy internal hardware), to allow longer exposures of the stars without getting unintentional trailing (smears) of stars.

The takeaway is that not all stacking is created equal. You need to know the context to understand what is meant by the word: stacking.

Focus Stacking / Auto Blend Layers

In Photoshop there is Edit -> Auto-Blend Layers -> Stack Images this is yet another kind of stacking (focus stacking) and despite the wording is NOT the kind of operation needed to ALIGN and Blend astro images. If you don’t believe us, give it a try and you’ll see it will do very weird things with your layers. Below are the same images as earlier. Note the bizarre masks it created to do the blending.

Edit -> Auto-Blend Layers -> Stack Images makes a mess. We told you so! Click to see a bigger image.


Aligned, Stacked Starry Landscape Images

While it would probably be better to make this a separate article in itself, we found it painful enough that we don’t recommend bothering – and yet we proceed to explain HOW to do it anyway!

If you want the cleanest possible images, you’ll – of course – want to reduce the overall noise  and bring out details by using many images instead of one. This approach is not all puppies and kittens. Here are some of the pitfalls:

  1. The direction of sky movement relative to the ground has a significant influence on the quality of the result (as well as the order chosen for alignment). In general, setting constellations are better than rising ones.
  2. Most of the existing tutorials will assume that you have a recent (CC) version of Photoshop with statistics and an an “Auto Align” that properly manages masked regions.
  3. Some of the tutorials we’ve observed are more cumbersome than they need be. There are plenty of hotkeys and mouse shortcuts to make the process go pretty quickly.
  4. More than 10 or so images can become quite demanding on machine resources.
  5. The complexity of your foreground will also affect the outcome. A clean, crisp separation between sky and land is preferable. Trees, poles, wires, and other things that extend through the sky are problematic.
  6. Lens distortion can also adversely affect the outcome.

Aligned Stacking Procedure

  1. Load all the photos as layers in Photoshop.
  2. Heal out airplane and satellite trails from each layer.
  3. Select all the layers and add to a group named “Sky
  4. Right click the Sky Group and duplicate the whole group as “Foreground”
  5. Select all the layers in Foreground.  Use Layer -> Smart Object -> Convert to Smart Object.
  6. Select Layer -> Smart Object -> Stack Mode -> Mean
  7. Duplicate Mean using Ctl-Alt-Shift-E (Command-Option-Shift-E on MAC). Label the newly created layer “Mean” and turn it off.
  8. Select all layers in Sky. Set blend mode to “Lighten” and observe the direction of star movement against the ground.
  9. Be sure the image with stars nearest the ground is at the BOTTOM of the stack. The bottom layer will be your base for alignment. You can drag layers around, or Layer -> Arrange -> Reverse may do the trick.
  10. Create a mask keeping as much of the sky as is easy to do but that DOESN’T include any ground  or fixed location objects. IMPORTANT: Be sure the mask doesn’t have holes in it, including at the bottom corners. Click the layer mask, hold down the Alt (Option) key and drag the mask to the next sky layer. Repeat until all sky images are masked with the same mask.
  11. Select the bottom layer and lock it  (Layers -> Lock Layers -> check Position -> Ok)
  12. Select all the sky layers.
  13. Chose Edit -> Auto Align Layers -> Auto
  14. When alignment is done, set blend mode for all sky layers to Darken. If stars are disappearing in the result image, that’s bad.
    1. If alignment is great everywhere, that is you have plenty of stars, you’re done. But it probably won’t be. So…
    2. Duplicate the current layers to a NEW document – call it whatever you want, but perhaps “Left looks good” makes sense.
    3. Open the history palette and click just above the “Align Layers” item (to restore to before the alignment was done). Lock the TOP layer (see item 11) and repeat steps 12-14.
    4. If a large portion of the image still has streaks in some quadrant, try undoing align, undoing the lock and re-aligning.
    5. If you’re still getting a significant amount of streaking you can also try Auto Align -> Reposition rather than auto.

      Q: Why do I have disappearing stars?
      A: The reason they are disappearing is because they are not aligned. In Darken mode, the darker sky “wins” out over the several stars. This COULD be a good thing in other situations, but not here!

      Q: If I went through the trouble of doing all this alignment, why is it still “off”?
      A: Photoshop isn’t optimized to align stars. Secondly, lens distortion makes a star move non-uniformly across the sensor. And third: stars at different declinations (celestial latitudes) travel at different speeds across the field. To eliminate streaks, the best solution is to track the sky.


  15. Take the aligned sky, delete all the layer masks. With all the aligned sky layers selected, create a smart Object.
  16. Do the same Stack Mode “Mean” trick for the sky smart object that you previously did for the foreground.
  17. The rest is pretty straight forward. Turn the foreground (mean) back on. Use a selection to reveal only the foreground and apply that to the Foreground Group.
  18. Adjust contrast, color balance, vibrance, etc. to your satisfaction.
  19. Save the kit and caboodle.

Does all this seem too complicated? Well, then perhaps you might consider using these tools instead. They do most of the hard work for you and they KNOW the difference between stars and foreground (usually because you help them know).

  • On a Mac: Starry Landscape Stacker – from the Mac App Store
  • On a PC: Sequator – do a Google Search to download it.

By the way there are many astro processing tools, like Deep Sky Stacker – but most/all of them expect that your images will have NO foreground or non-moving objects like wires in them.

Not Eclipsed!

Published: February 6, 2018

The total Lunar Eclipse of February, 2018 reminded me of my travails from my first effort to shoot an eclipse in 2010.

My First Eclipse Attempt: 2010

In December 2010, I was crestfallen to see the weather reports. The last total eclipse of the moon visible from North America until 2014… and the weather everywhere within a reasonable 3-4 hour drive was predicted to be 90% clouds and worse. It seemed my eclipse was going to be eclipsed by cloud cover.

At about 9:15 PM, PST on December 20th, however, I looked up and saw… THE MOON!  Sure, it was scintillating in a little sucker hole playing with me. But I decided to play along. I hastily hauled out the Canon 5D Mark II, the 70-200mm f/4 IS L lens, the 1.4x Telextender, and the Gitzo carbon fiber tripod. Why those? Because that’s what I found first.

My equipment was scattered about in my office still recovering from the wet weather from earlier in San Jose. Indeed, I did not find the batteries for my Canon 50D camera.

By the time I got set up, I realized that the moon would very soon be contacting the earth’s umbra (darkest part of the shadow). So I quickly got to shooting what I could. Never mind that it was cold and I was not dressed properly.  Soon enough the clouds would come and I could dart into the house to hurriedly collect what I was missing.  The first shot I got was with the moon in the earth’s penumbra. Not particularly remarkable, unfortunately.

Through various breaks in the clouds I was able to get photos from first umbra contact all the way up to totality. Including a serendipitous shot of an airplane headed, probably, to the San Francisco airport or some other place to the north west.

Airplane Transits the Partially Eclipsed Moon
Airplane Transits the Partially Eclipsed Moon

What settings did I use for these shots? f/7.1, ISO 200, and 1/400 of a second exposures. Why so fast? Because, my friends, the moon is BRIGHT. Even partially eclipsed, even already in earths penumbra it is a big bright object. Shooting the moon is a definitive case where your camera absolutely cannot get the right exposure if left to itself. A good exposure must be manually set. I arrived at my settings by a few quick trials. I started at about 1/200th at f/5.6 and noticed that I was getting some over exposed areas (on my LCD screen the overexposed pixels blink white). I then decreased the aperture and continued to tweak the focus.

I wanted the moon images to be as well exposed as possible – especially knowing that the thin clouds were going to dim the image. My goal was to get detail in the moon, I did not care about the clouds or stars. In fact it is impossible – except at a very slender crescent or during a total eclipse to get detail in the moon AND also show stars in the sky. Why? Because the moon is so, SO bright.

I definitely made a slew of mistakes. The most significant one is that I should have put the telephoto lens on my 50D body which is a 1.6 crop camera. Had I done that all my moon images would have been about twice the size of what I actually got. Not having my camera all packed away in my bag meant some lost opportunities here.

I also thought  that perhaps the 5D would have been a good choice to get a sequence of shots showing the progression of the eclipse. The idea was to get the moon in the bottom corner of the frame and take a series of shots as it moved to the upper left of the frame. This also did not work for several reasons. The first problem was that the cloud “holes” came at irregular intervals – so spreading them across the frame evenly was not going to happen. The second problem was purely my failure to correctly guess the path the moon would follow in the sky.  Had I been a little smarter I’d have switched lenses when I realized the timelapse path was not going to work. But instead I tried again a few times.

I also realized that when the eclipse was total, the moon was going to be quite dim and the superior high ISO performance of the 5D II was needed. For the totally eclipsed shot, the ISO was ramped all the way up to 1600 and the exposure dropped from 1/400 to 1/6 of a second. That is a HUGE difference. The slower exposure meant that details in the moon would be blurred and the stars at this telephoto range would become dashes rather than dots.

Jewel [C_029690]
Nearly Total – With enough bright area left to form a halo in the clouds

Epilogue:  February, 2018

Sadly I was NOT much better prepared. After studying the weather forecasts, I headed to the coast where it is often really yucky with fog, low clouds, and on-shore winds that bring dampness and salt spray. It was surprisingly clear. My goal was to take a series of shots showing the progression of the eclipse ending at sunrise with the moon hovering over the Pigeon Point Lighthouse. I had done all the calculations as we cover in our Catching the Moon Webinar. (And also somewhat described here)

I imagined something like this effort, but better done.
Plan C: San Jose City Hall Eclipse Sequence

As it came about in 2014, we had to go with plan C due to weather. So I was excited that the weather forecast for the coast was much better in February, 2018. Some oversights on preparation conspired against me. I had not jotted down the proper GPS location and on site I had no cell signal, so couldn’t (re)calculate the spot. That left me wandering about trying to find the little tree and path that was featured on the satellite view… and NOT finding it.

Instead I ended up wandering into a thicket of brush that had an abrupt downward slope. That was fall number 1. Several efforts (and falls) later I tried setting my tripod down THROUGH the gorse all around… only to snap the leg off of my tripod. Now I needed to take  trek back to the car for my backup tripod. (Fortunately I had one!).

Since I got a late start, I scrambled to try to get a couple of series of panoramas on which to overlay the moon trajectory. However the moon was already in complete eclipse by the time I had everything set up. It was only then that I realized I was not getting the details I wanted out of the moon. I was using a 70mm f/4 lens, and the long exposures were streaking the stars and blurring the moon. So while I did get a FEW shots, they weren’t the ones I had imagined. My problem, in a nutshell, was that I was trying to get the moon AND the stars … which I did, but at the cost of streaking and blurring.

Orb to Rule the Night

By the time twilight started to appear, it was obvious that my location was about 1/4 mile distant from where I wanted to be… the little tree that I thought might form the right edge of my panorama was far off. The moon was NOT going to land anywhere near the Pigeon Point Lighthouse, so I packed up and ran up Highway 1 closer to the calculated location. I had to abandon the sequence plans, throw on the big tele-extender and HOPE the moon would survive visibility through the now obvious off-shore fog bank. Of course it didn’t. It fizzled as it got near the target.  I did get a consolation prize of sorts, though. This image hit 80 THOUSAND views in a few days – becoming my most popular photo on Flickr EVER. Sadly it’s not the image I imagined.

It's A Little Bit Broken
Photo from the end of the total eclipse of February, 2018

What Did I Learn?

To get a decent eclipsed moon shot with details, either you need a very fast telephoto lens, or to use a mount to track the moon. I also need to be willing to lose more sleep. I woke up at 3:00 AM, but the 90 minute drive meant that the umbral (dark part) of the eclipse would be starting as I arrived.

I also realized that if I’m going to spend the better part of a day mapping out the moon trajectory toward a landmark like the Pigeon Point Lighthouse, I’d do well to record some GPS locations (where to park, where to stand), and even get a Google map pre-downloaded.

Hopefully you, dear reader, will learn from my mistakes because you won’t have enough time to make them all yourself!

Exploring Night Photography: Lesson 6 BEST TIPS

Band of Techies by Steven Christenson on 500px.com

Twilight Panorama of the San Francisco Bay

Last week we talked about photo processing.  This week is the last week of the in-person course.

The topics covered in class included Astrophotography, suggestions on what equipment NOT to get for Astrophotography. We also discussed the limitations of Lightroom and Photoshop (see Lesson 5) because we did not cover them all in the last class.

To conclude our lesson series we present our greatest tips.  Many of the tips you may be familiar with – especially if you have been with us on a workshop. Some tips will be a surprise.

Our Best Night Photography Tips

  1. Shine a bright flashlight through your viewfinder at night and it will show you what is in your shot. Much easier to figure out where the edges of your frame are when it is too dark to see well.
  2. A flashlight will not illuminate the sky where your shot is constrained by your lens, but a bright green laser through the viewfinder can accomplish that!
  3. Put glow sticks or LED slap bracelets around your tripod at night. Not only can you find your gear easily, but others are less likely to trip over it.
  4. Have a bluish LED light that you need to make less “cold”? Bounce it off the palm of your hand… or a warm colored shirt.
  5. Want to see well in the dark? Don’t wear a head lamp! Shadows and contours are hard to see when the light is coming from close to your eyes. Instead keep a DIM light at waist level. Bright lights ruin your night vision. And headlamps make it painful to talk to one another… you ruin their night vision when you look at them.
  6. Before you spend the effort traveling for night photographs, consult the weather and the moon phase.
  7. It is astonishing how much you can pre-plan a shot without having to go the location… hint: learn to use Google Maps + Street View!
  8. Don’t overlook the hundreds of tips we have for you here on this site… the search box is your friend.
  9. Dark skies are good… but better is to know which direction you want the sky to be dark so you can make the right compromises.
  10. Sometimes being behind a hill is a great help to prevent unwanted stray light.
  11. Want to photograph (or see) the best part of the Milky Way? You need to know when it is up. A planisphere (rotating star chart) is your best bet.
  12. Velcro is a great way to keep things handy and secure on your tripod. Velcro your intervalometer to your tripod.
  13. Lens hood – use one all the time to protect your lens and prevent stray light from causing glare.
  14. Do not use any filters – especially not a clear or “ultraviolet” filter. All filters make your image less desirable by causing extra surfaces that can reflect light and cause glare. Our only exception to this rule are 1: polarizing filters – which are useless at night, and 2: a filter to seal your lens in really nasty environments like rain and blowing sand.
  15. Test your tripod stability before you move away from it. If your tripod is secure, take a few steps back and make sure the center column is vertical.  It is common to set a tripod up so that it leans in a way that makes it vulnerable to a fall.
  16. Another tripod tip: on a hill or slope, put two legs on the downhill side, one on the uphill side.
  17. Short straps (or no straps) on your camera is better for stability if there is any wind at all. We have personally seen cameras thrown over by wind gusts.
  18. Do not cheap out on a tripod. A sturdy tripod is more valuable for night photography than a “better” camera.
  19. The histogram is your friend. Be sure to check it before you conclude your shot is a good one.
  20. If your tripod has a hook below the center column hang your camera bag on it for even more stability. Be sure you’ve taken out all you need before you start shooting. Oh, and this may NOT work well if it is really windy or your pack is light.
  21. Study the place you plan to go during the daylight. It is not fun falling in holes or stepping on nasty things while wandering in the dark.
  22. Take a friend along for added safety, camaraderie and comfort. Also you do not have to outrun a bear, you just have to outrun your friend. 😉  [Do NOT try to run from a bear, by the way. That just makes you look tastier]
  23. A ball head works a lot better for night photography than a pan-tilt head. But get a sturdy head! It is useless having a sturdy tripod with a head that can not stay put.
  24. If there is anyone who may care: tell where you are going and when you expect to be back. Stick to the plan, too.
  25. Do not assume you will have cell service – some of the most amazing places to photograph have no cell coverage at all. Oh, and your battery might die.
  26. Overshoot. It is so much better to have two or three times as many shots as you think you will need than to find out you did not even get one quite right.
  27. When shooting sequences or panoramas… use your lens cap between sets so you can figure out when one set ends and another begins. Take it one step further and do what we do: use your hand forming an E, N, W, or pointing down to indicate the direction you are facing when you take the shot.
  28. Dark gloves make great “emergency stray-light reduction” devices – and they can keep your hands warm, too.
  29. It will always seem colder at night than the temperature might indicate. Dress in layers.
  30. Planning to leave your camera shooting for a long sequence and walk away? Use a GPS to record the camera location (you can do this using most cell phone map software, too).
  31. Respect people and their property. Ask for permission. You may be amazed how much farther courtesy and thoughtfulness will get you than being an intentional trespasser.

Have a tip you think is really super helpful? Please comment below!

Last Week’s Homework

Photo edit a “better” foreground into a star trail image.

Final Homework

  1. Comment below with what you’d like to learn about next.
  2. Get creative and leave us a comment below with a link to your super image.
  3. Comment below with the best tip you have learned about doing night photography.

 

Heaven Light by Steven Christenson

Milky Way and Waterfall – we talked about how to get the Milky Way aligned where you want it.

Exploring Night Photography: Lesson 3 – Gear

Two weeks ago in class we covered basics (what is a photograph, using manual settings) Last week we learned a bit about noise, and its primary causes – temperature being the principle problem. And we explored different creative directions under the umbrella of night photography. We also got outside under a half-full moon (first quarter) and shot on campus. And learned a little about the night sky.

This view is southwest. From left to right are Canis Major, Orion and Taurus. The moon is off the top edge.

This view is southwest. From left to right are Canis Major, Orion and Taurus. The moon is off the top edge. The glow in the lower right corner is the glow bracelet on one of the student’s tripods. The sky remains blue due to the moonlight. Settings for this shot are ISO 800, f/2.8, 10 seconds, 20 mm on Canon 5D II.

Now it is time to talk about gear. Fortunately we already wrote a nicely detailed article about gear. Take a look here. We even updated it recently.

Too busy to read the details? That’s a shame, but here is the super quick summary in order of importance:

  1. GOOD tripod.
  2. Night photography friendly lens (wide angle recommended)
  3. Decent camera body with an optical viewfinder. Full frame preferred, but not necessary.
  4. Layered clothing and good shoes, including lightweight gloves (G) – and heavy gloves in cold season.
  5. Sturdy camera bag
  6. Extra batteries and memory cards
  7. An intervalometer (1), and extra batteries (2)
  8. Headlamp (B) and flashlight assortment (C, 3, 6)
  9. Other needful things: clear shower cap (A), lens cloth, hand cloth.

What About Other “Gear”?

MiscGear
Here is what is usually in our bag besides the camera gear.

  • (H) Glow bracelet/stick to mark the camera location (we have just started experimenting with other methods, too, like the LED band (4).
  • Hand warmers (F and 5) and rubber bands (G) for dealing with dew formation
  • Creative lights – bulbs, keychain lights,  and cord (3, 4, 6, 7, 8, 9)  Item 7 is a green laser pointer.
  • Insect Repellant  (E)
  • Gaffers Tape – flat black duct tape (L). We don’t take a whole roll though!
  • A smart app that shows the positions of the stars, planets, and bright satellites. Also helps if it shows meteor showers.
  • A smart app that shows the location(s) of sunrise, sunset, moonrise and moonset.
  • A game or two on the smart phone to pass time.
  • An external battery to keep our smart phone juiced (5) and the appropriate matching cord.

Before We Leave We Also Use the Following

  • A star map (planisphere). On our desktop, we favor Stellarium, but it is a little geeky to use well. On iOS we like Sky Safari, Star Map.
  • Weather prognostication tool
  • Sunrise/set Moonrise/set predictions.

 

Last Week’s Homework

We asked you to pick a creative direction. Here are some shots our students took including “semi transparent” you, moving lights.

XNP_Alex_assignmentsTop: f/4 1/30, 500 ISO, 20mm; Lower photo: f/4,  1/4, 1600 ISO,  20mm. Bottom was from moving the camera body

 

XNP_Tracie_Assignment

XNP_Troy_assignment

 

This Week’s Homework

  1. Use the light you were given in class to write a message or draw an image in light.
  2. The moon is full, if you didn’t work out settings for capturing the moon. Now is another chance. If you did work out the settings, compare them to your last shot when the moon was half-full. Notice anything?
  3. Find a way to make a strong white flashlight a different color. Use the colored light to illuminate your foreground. Your light may have to be really bright to compete with moonlight.
  4. If you are using a “white” LED flashlight, you’ll notice it is significantly cold (blue). Can you think of a way to make it a warmer color?
  5. Is there any “Other Gear” listed above that intrigues you? E.g. what can you use Gaffers Tape for?

Next… Lesson 4.